Exploration Of An Anaerobic Microbial Sulfur And Nitrogen Synergistic Metabolic System And Influencing Factors

Anaerobic ammonia oxidation(anammox)is a nitrogen removal technology that had received a lot of attention in recent years,and its characteristics of no aeration and no added carbon source meet the requirements of contemporary green development.As the research progressed,it was found that the metabolism of anammox bacteria was diverse,i.e.,anammox bacteria could use not only the traditional NO2-as electron acceptor,but also SO42-,Mn4+,Fe3+,etc.to oxidize NH4+.The wastewater discharged from chemical,food and pharmaceutical industries contained certain concentrations of SO42-,S2O32-and NH4+.If the synchronous removal of sulfur and nitrogen could be achieved by biological methods,it would further reduce the cost of water treatment and also broaden our understanding of anammox process.It has been showed that SO42-acts as an electron acceptor and NH4+as an electron donor,both of which can undergo reactions similar to anammox in the presence of microorganisms.In this study,NH4+was used as the nitrogen source,SO42-and S2O32-were used as the sulfur sources,respectively.The differences in the simultaneous sulfur and nitrogen conversion were compared in anaerobic baffled reactor(ABR)under different substrate conditions.The different S/N settings(1:4 for S1 stage,1:2 for S2 stage,and 3:4 for S3 stage)were used to further analyze in depth the reactions occurring in the different operation stages and in the different compartments of the ABR.The main conclusions of the paper were as follows.(1)The anaerobic microbial sulfur and nitrogen synergistic metabolism system was successfully constructed in ABR reactors.The NH4+-N removal efficiency of the sulfate and ammonium-based reactor(R1)reached 50.69%in 55 days.The NH4+-N removal efficiency of the thiosulfate and ammonium-based reactor(R2)reached 52.30%in 62 days.(2)Sulfate reducing ammonia oxidation,sulfur autotrophic denitrification and sulfate reduction processes occurred in R1,which was demonstrated by batch experiments.(3)Sulfite was generated from thiosulfate in R2 by microbial activity.Sulfite reducing anaerobic ammonia oxidation,sulfite oxidation and sulfate reduction processes occurred in R2,which was demonstrated by batch experiments.(4)In the anaerobic microbial sulfur and nitrogen synmetabolic system without carbon source,the molar ratio of SO42--S to NH4+-N simultaneous conversion consumption was 1:2.41.The molar ratio of SO32--S to NH4+-N simultaneous conversion consumption was 1:1.33.(5)Thiosulfate promoted the expression of the sulfur reduction functional gene dsrB more than sulfate,and the dsrB gene was approximately twice as abundant within R2 as within R1.The abundance of the sulfur oxidation functional gene soxB increased substantially within the three or four compartments of R1 and R2,with an approximately five-fold increase compared to the original mud.(6)The change of S/N had a significant effect on the removal of SO42-and NH4+in the reactor.The removal efficiency of SO42--S was 59.67±2.34%,84.50±0.65%and 71.97±0.98%in S1,S2 and S3 stages,respectively.The removal efficiency of NH4+-N was 54.36±0.98%,90.81±1.21%and 74.65±2.16%in S1,S2 and S3 stages,respectively.And the best simultaneous removal of sulfur and nitrogen in the reactor was achieved at the S/N ratio of 1:2.(7)The morphology of the inoculated sludge was affected to different degrees by different sulfur sources,while the granular sludge in the R1 reactor was stable and the R2 reactor showed a mixture of flocculent and granular sludge.(8)High-throughput analysis showed a higher diversity of biological communities within R2 than in R1.Chloroflexi was in high abundance in the first and second chambers of the ABR reactor.Syntrophobacter had elevated abundance in the third and fourth chambers of R1 and R2,and its relative abundance was approximately twice that of the first two compartments.The average abundance of Bacteroidetes_vadinHA17 was 14.63%in the four chambers of S1,11.03%in S2 and 5.99%in S3.Bacteroidetes_vadinHA17 was more suitable for living in a low S/N ratio environment.The abundance of Planctomycetes increased with increasing S/N,with the highest abundance of 10.99%in the third compartment of S3.